Research on Yaw Stability Control of Unmanned Vehicle Based on Integrated Electromechanical Brake Booster

The Electromechanical Brake Booster system (EMBB) integrates active braking and energy recovery and becomes a novel brake-by-wire solution that substitutes the vacuum booster. While the intelligent unmanned vehicle is in unstable state, the EMBB can improve the vehicle yaw stability more quickly and safely. In this paper, a new type of integrated EMBB has been designed, which mainly includes two parts: servo motor unit and hydraulic control unit. Aiming at the dynamic instability problem of intelligent unmanned vehicle, a three-layer vehicle yaw stability control structure including decision layer, distribution layer and execution layer is proposed based on integrated EMBB. Firstly, the decision layer calculates the ideal yaw rate and the side slip angle of the vehicle with the classic 2DOF vehicle dynamics model. The boundary of the stable region is determined by the phase plane method and the additional yaw moment is determined by the feedback PI control algorithm. Secondly, the distribution layer optimally selects the wheel with the highest differential braking efficiency and assigns the brake pressure to the corresponding wheel based on the additional yaw moment calculated by the decision layer. In the execution layer, the servo motor unit employs the position-current double closed-loop PI algorithm to achieve rapid building-up pressure and then precise control of the single-wheel pressure is achieved by controlling the electromagnetic valve of the hydraulic unit. Finally, with the dSPACE products, we built the hardware-in-the-loop (HIL) test bench based on integrated EMBB. The proposed control strategy is verified by using Similator to run CarSim in real-time and MicroAutoBox to run the algorithm. The HIL experiment results show that the yaw stability control algorithm based on integrated EMBB can effectively restore the unstable vehicle to the stable driving zone and enhance the driving safety of the complete vehicle.